I hope the past few blog posts have encouraged you to find a copy of Tom Vanderbilt’s book Traffic. The number of insights it offers into traffic safety is breathtaking.
Once again let me spotlight a seemingly simple Vanderbilt observation that, on closer examination, is more complicated and also important for teen drivers and parents to understand: Judging the speed of cars is difficult — both the ones we are driving and the others on the road with us (p.93).
Here in Connecticut, this difficulty in judging speed was the prime cause two years ago of a crash in which two teens died. A police officer in hot pursuit was driving on a four lane arterial road next to a shopping mall at an estimated 90 MPH. The teens began a U-turn across the road. Mostly likely they saw a vehicle approaching, but had no idea, and no way to know, that it was going so fast, so as they made their leisurely U-turn, the police vehicle reached their location much more quickly than they expected, and hit them broadside. The officer most likely had trouble judging how long it would take the other car to turn.
Vanderbilt offers two critical insights into judging speed. The first is that the higher the driver is — that is, the higher the driver’s eye level in relation to the road — the better able the driver is to judge how much ground the car is covering — not necessarily miles per hour, but at least the rate of speed and how long it will take to go from Point A to Point B. The second is that it is easier to judge the relatively speed of a vehicle going in the same direction as your car and much more difficult to perceive the speed of a car or truck going in the opposite direction, especially on a narrow road. This second insight explains in part why two lane roads, one lane in each direction, are generally the most dangerous, as compared to limited access highways where the only vehicles we are in contact with are those going in the same direction.
Two take-always for parents of teen drivers from these observations: First, vehicles with driver eyesight elevations that are low to the ground are more problematic for new drivers — they add an element of risk, greater difficulty in judging speed. Second, when parents, acting as air traffic controllers, plan a route for their teen drivers, avoiding narrow two line roads where judging speed of oncoming vehicles will be necessary is a good planning tool.